I have seen this "issue" since 8.X, and has continued into 10.X and nothing has been done to correct it. When saving a MXD or PDF (or any other format from ArcMap, it always reverts back to the last saved location. For me this is a problem since I have to navigate into many drives (from X: drive, to Y: Drive, back to X: Drive) and different projects and folders. Will there be any improvements in where a MXD (Saved As), or PDF will be saved. Can ESRI please fix this "bug" so that when we "SAVEAS" updated files and PDF's that it is automatically mapped to the same folder the MXD & PDF is mapped to and not the previous project.